Vitamin D and People With Skin Cancer: The Pharmacist's Perspective

I come from a family of pharmacists. My father, my oldest brother, and my oldest brother’s wife are all pharmacists. I am aware of the key role a pharmacist plays in healthcare, but I am not sure everyone else is. I wanted to write an article with pharmacists, so they could show their expertise and provide practical knowledge for those of us on a skin cancer journey.

I had the idea of getting a pharmacist to shed some light on the need for vitamin D and its use in those of us who have been restricted to limited sun exposure. I have been out of the sun for years, and I have been taking a daily vitamin D supplement during that time. When I get blood work done, my doctor always monitors my vitamin D level. However, beyond that limited personal knowledge, I know essentially nothing about vitamin D.

I interviewed two pharmacists, Colin Cabelka, PharmD, and Joseph Martinez, PharmD. They are both first-year pharmacists who are completing a residency program at Campbell University. They were kind enough to share their knowledge on the topic in the following question-and-answer dialogue.

What do pharmacists do for patients?

A pharmacist’s main role as a drug expert is to ensure the safety of medicines that doctors prescribe for patients. Certain medicine combinations can be dangerous. It is up to the pharmacist to act on medicines that may be hazardous to a patient.

It is also a pharmacist’s responsibility to educate people on how to correctly use medicines and tell them about any side effects. Many pharmacists go beyond these roles as prescribers and work closely with other healthcare providers to optimize medication therapy.

What can pharmacists do for people with skin cancer?

Some skin cancer medicines require extensive education on their use and side effects. Pharmacists are a great resource for questions about your treatment and any potential interactions with medicines unrelated to skin cancer treatment.

What is vitamin D?

Vitamin D’s most studied purpose is in the role of calcium regulation in your body. Vitamin D helps increase the absorption of calcium from your diet and maintains blood levels of calcium to promote bone formation.¹

How is vitamin D absorbed?

Vitamin D can be absorbed from food or made in your body with a chemical reaction involving skin exposure to sunlight. Since sunlight exposure increases skin cancer risk, most people with skin cancer may need to absorb their vitamin D from food or supplement sources. Vitamin D is a fat-soluble vitamin. This means it is best absorbed when taken with fatty foods or the largest meal of the day.¹

How much vitamin D should I be getting?

The current recommended daily allowance (RDA) set by the National Institutes for Health is between 400 and 800 units of vitamin D per day. This amount assumes you are not getting any vitamin D from sunlight exposure. This is the needed food or supplement amount to maintain your normal levels of vitamin D.¹

What kind of food contains vitamin D?

Few foods naturally contain vitamin D. Natural sources include fatty fish, cod liver oil, and mushrooms exposed to sunlight. Since there are few natural sources, many foods have vitamin D added to them (fortified). Milk, milk substitutes, and breakfast cereals frequently have vitamin D added to them.¹

Many people supplement vitamin D if they cannot expose themselves to sunlight. You can estimate your vitamin D intake from food using resources from Dietary Guidelines for Americans.

What can happen with low levels of vitamin D?

Vitamin D deficiency in children can cause rickets. This disease is much less common since vitamin D has been added to food products in the United States. But it still occurs in breastfed children lacking sun exposure.¹

Osteomalacia and osteoporosis are diseases that can occur later in life involving loss of bone strength and increased risk of bone fractures. Risk for these diseases can be increased with long periods of severe vitamin D deficiency.¹

Who is at risk for low levels of vitamin D?

People with darker skin tones are more at risk for low vitamin D than people with light skin. Dark skin protects against harmful radiation from the sun but also blocks vitamin D formation from sunlight.²

Skin cancer with little sunlight exposure, colitis, older age, and obesity are also at risk for deficiency. The risk for deficiency increases during winter, when sunlight intensity is decreased and people spend more time indoors.²

Should people with skin cancer take vitamin D?

People with skin cancer who are actively avoiding sunlight may be at more risk for deficiency. Obesity, older age, colitis, and dark skin color may also increase your risk. All people with skin cancer, especially those with additional risks, should get their vitamin D levels tested and consider supplementation.²

I’m vitamin D deficient. Am I at risk for osteoporosis?

Osteoporosis is a bone disease that develops most commonly in women after menopause. It results in low bone density and an increased risk for fractures. Most studies find that severe deficiency of vitamin D (<12 mcg/mL) is a high risk for osteoporosis.²

But osteoporosis risk cannot be explained by vitamin D levels alone. For example, studies show that Black people are more likely to have low vitamin D levels. However, this population has lower osteoporosis and bone fracture risk compared to white people.³

People naturally have varying vitamin D levels, and there has been debate on what levels of vitamin D should be treated. Women should discuss bone density scanning with their doctor after menopause to determine their risk for osteoporosis.

I’m thinking about supplementing with vitamin D. What risks or side effects are there?

A total food and supplement intake of 4,000 units per day or less of vitamin D is considered safe long-term. Some supplements contain more than this amount and may be safe but are less studied.¹

It is possible to overdo supplementation using higher than recommended doses. This can cause serious toxicity. These cases are rare, but people should ask their doctor how long they should supplement and measure their vitamin D levels.³

There is a small increased risk for kidney stones with vitamin D supplementation. People who have had issues with kidney stones in the past should ask their doctor if supplementation is right for them.³

Should I supplement vitamin D during pregnancy?

You may need to supplement vitamin D after talking to your doctor. Many pregnant people will not require it, especially if they are already taking a prenatal vitamin since most products contain 1,000 units. If you have other risk factors, a doctor may test your vitamin D levels and decide if you need more supplementation.⁴

What types of vitamin D supplements are available?

Vitamin D comes in different forms, including tablets, capsules, soft gels, and gummies. They are made by many companies, which can make it hard to make a selection.

Overall, we recommend products that have a “USP Verified” logo, which has been tested by the US Pharmacopeia. This group sets the standard for the quality of medicines and supplements. The logo verifies that the product has been deemed not only safe but effective.

What is the difference between vitamin D2 and vitamin D3?

Vitamin D2 (ergocalciferol) and D3 (cholecalciferol) are both converted to active vitamin D inside the body. Both can be found naturally in the diet, while D3 can be made when your skin is exposed to sunlight. When given as a supplement, there is no difference (good or bad) for your body, as they work in similar ways to regulate calcium levels.⁵

What other purposes is vitamin D used for?

Vitamin D can also be used as a combination treatment to increase calcium levels in people who are at greater risk for deficiency. This includes people with kidney disease, hormone disorders, thyroid disorders, etc.⁵

Vitamin D receptors are found in different cell types around the body, including in the immune system. The location of these receptors has suggested that vitamin D may play a role in fighting infections and preventing other health conditions.¹

There are many studies into other roles of vitamin D, such as COVID-19 severity. But many studies are not strong enough to draw reliable conclusions. Vitamin D, vitamin D levels, and their link to diseases are hard to study because vitamin D intake is closely tied to skin color, diet, level of sun exposure, and genetics.⁶

About the pharmacists

Colin Cabelka, PharmD, is a first-year pharmacist who is completing a residency program at Campbell University and Josef’s Pharmacy in Raleigh, NC. He completed pharmacy school at the UNC Eshelman School of Pharmacy and earned a bachelor’s degree in microbiology from the University of Wisconsin-Madison. Colin’s interests are in independent community pharmacy, long-term care, and specialty pharmacy. Outside of work, Colin disc golfs, snowboards, rock climbs, and enjoys photography.

Joseph Martinez, PharmD, is a first-year pharmacist completing a PGY1 residency at Campbell University and Walgreens Pharmacy. He completed pharmacy school at the University of Colorado Skaggs School of Pharmacy and Pharmaceutical Sciences, and a bachelor’s degree in biochemistry from the University of New Mexico. Joseph’s interests include ambulatory (primary) care and specialty pharmacy, both focusing on diabetes, cardiology, and anticoagulation. On his days off, he enjoys reading, listening to podcasts, watching the Atlanta Braves, playing video games, and spending time with his wife and two dogs.